Modular curvilinear staircase

ABSTRACT

Provided as a curved staircase which extends between upper and lower levels of a building structure. The building structure has a plurality of spaced vertical wall studs. The curved staircase comprises a plurality of step modules each including a side panel, a front riser and a back riser. Each of the step modules is disposed in stacked relationship to one another to define a plurality of module joints. Each one of the step modules includes a tread which is mounted on the back riser and side panel as well as on the front riser of the next lowest step module. Inner and outer reinforcing panels are disposed in overlapping relationship to the step modules in order to interconnect the step modules.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

The present invention relates generally to building construction and, more particularly, to a uniquely configured curved staircase that is constructed of individual step modules that are pre-manufactured off-site and which are then assembled in stacked arrangement at a job site and inter-connected to framing of a building structure.

In building construction and, more particularly, in home construction, the installation of a curved stairway adds to the aesthetic appeal of a home interior. Furthermore, homeowners and builders realize that a curved staircase is generally a good investment in that a curved staircase may increase the home's resale value compared to value added by a simple, straight staircase. Unfortunately, prior art curved staircases are generally more expensive than straight staircases. Such increased expense is due in large part to the cost of forming the curved portions of the curved staircase. Furthermore, the installation of a curved staircase requires a higher degree of skill and is sometimes comparable to the high level of skill required in cabinet making.

The increased expense is also due in part to the time consuming manner in which such curved staircases are installed. For example, prior art methods of curved staircase construction include trial-and-error cutting and fitting of the staircase framing as well as fitting of the individual components of the staircase. Prior art building methods are also typically performed at the job site and are built into the structure.

In such methods, an outer wall is framed with studs and an inner wall is then framed with the stringers being attached to the studs of the inner wall. Risers are then cut and assembled into individual steps to tie the outer wall to the inner wall in order to form the curved staircase steps. Unfortunately, such conventional method for curved staircase construction is extremely time consuming. Furthermore, such conventional building method is highly dependent upon skilled labor and the availability of specialized tooling required to produce a staircase that meets precise tolerance requirements mandated by local and national building codes.

In an attempt to reduce the time and cost required to construct curved staircases, several manufacturers have developed pre-assembled completed curved staircases that are assembled at a factory and shipped as a unit to the job site. Such preassembled staircases are then installed by interconnecting the staircase at strategic points to the building structure. Unfortunately, due to the difficulty in controlling the tolerance of the building structure to which the completed staircase is to be connected, problems with fitment may occur. In addition, generation of excess material wastage, schedule conflicts such as with framers, and issues in meeting building code requirements may develop.

Furthermore, the shipping of an entire completed curved staircase to a building structure many miles from the factory may entail significant logistical problems and may incur great expense. Furthermore, the cost of pre-manufacturing such a curved staircase may run into the many thousands of dollars even prior to final installation into a building structure. Finally, such prior art building construction of curved staircases may result in problems with the structural integrity of the curved staircase and, more particular, problems associated with the connection of the curved staircase to upper and lower levels of the building structure. A common problem that may develop later with curved staircases of the prior art is that the staircase may develop squeakage due to loosening of joints over time.

As can be seen, there exists a need in the art for a curved staircase that can be constructed within various building code limits. Furthermore, there exists a need in the art for a curved staircase that can be pre-manufactured in modular form and shipped as individual components to a job site. Additionally, there exists a need in the art for a curved staircase that can be manufactured to precise tolerances using specialized machinery in climate controlled conditions of a pre-manufacturing facility. Also, there exists a need in the art for a curved staircase that can be initially designed to be compatible with the building structure using computer aided design techniques in order to avoid costly errors during final installation. Finally, there exists a need in the art for a curved staircase that is of low cost and that can be easily installed in a drastically reduced amount of time.

BRIEF SUMMARY OF THE INVENTION

The present invention specifically addresses the above referenced needs associated with curved staircases. More specifically, the present invention is a uniquely configured curved staircase that is constructed of individual step modules that are pre-manufactured offsite and which are then assembled in stacked arrangement at a job site. Advantageously, the step modules of the present invention may be manufactured using unskilled labor and with precision tooling and machinery in order to reduce costs and assembly time.

The curved staircase comprises a plurality of the step modules, a plurality of treads mounted on the step modules and a plurality of inter and outer reinforcing panels disposed in overlapping relationship to interconnect the step modules. The curved staircase extends between upper and lower levels of a building structure and is interconnected to framing that is comprised of vertically oriented wall studs extending between the upper and lower levels. The inner side of the curve staircase is generally free standing and supported only at the upper and lower levels of the building structure.

Each one of the step modules is preassembled and pre-manufactured using specialized tooling. Each one of the step modules is comprised of at least a side panel, a front riser, and a back riser extending outwardly from the side panel. A side panel may be generally articulately (i.e., curved) and having an outer conduct surface and an inter conduct surface. To achieve the radius of curvature of the side panel, a plurality of laminated members are layered upon one another in curved relationship. The laminated members may be formed of bonded particulate material fabricated from cellules fiber, shredded paper, wooden particles, sawdust and various combinations thereof. The particulate material of the laminate members may be bonded together via a matrix resin. Under sufficient temperature and pressure, the side panel may be formed having the desired radius of curvature complementary to the curved staircase.

Each one of the side panels is constructed at a riser height which is generally equivalent to a height of the back riser. The front and back risers are disposed in overlapping relationship to one another and are generally positioned upon the outer convex surface.

The back riser forms the aft mounting member for the tread while the front riser forms the forward mounting surface for the tread of the step module located immediately above. Upper edges of the side panel and the back riser are preferably flush with one another such that the tread may be evenly supported thereupon. The front riser has an upper edge which extends past the upper edges of the side panel and back riser. In this manner, the front riser determines the height of each one of the steps of the curved staircase. The side panel and back riser are formed at a riser height while the front riser is formed at twice the riser height.

Each of the step modules is disposed in stacked relationship to one another and are also angularly spaced with respect to one another. The angular orientation and spacing between adjacent ones of the step modules is preferably equivalent to the spacing between the wall studs of the building structure in order to facilitate interconnection of the step modules thereto. A module joint is formed between each one of the step modules. A plurality of tapered treads are mounted on upper edges of the back riser and side panel and are mounted on an upper edge of the front riser of the next lower adjacent step module. The step modules are angularly spaced in order to create a suitable area for the tread mounting. Each one of the treads is preferably mounted so as to be abutted up against the front riser of the step module upon which the tread is mounted. The front riser of the next lower adjacent step module serves as the mounting surface for a forward portion of the tread.

Manufacturing grade plywood is preferably utilized for fabricating the tread and the front and back risers. The treads may be fabricated of any material that is sufficiently suitably hard. In this regard, exemplary materials include, but are not limited to, manufacturing grade plywood or any hard wood such as oak, mahogany, cherry and birch. Following the stacking and angular orientation of the individual ones of the step modules, a plurality of inter reinforcing panels is then disposed in overlapping relationship to the inner concave surfaces of the side panels. Preferably, each one of the inner reinforcing panels overlaps at least one of the module joints in order to interconnect adjacent ones of the modules. Preferably, the inner reinforcing panels abut against one another in order to form a plurality of inner panel joints which are likewise horizontally oriented and are staggered in relationship to the module joints.

A plurality of the outer reinforcing panels may then be disposed in overlapping relationship to the inner reinforcing panels and preferably extend across the inner panel joints. Each one of the outer reinforcing panels preferably straddles at least on end, more preferably, two of the inner panel joints. In this regard, the outer reinforcing panels form a plurality of outer panel joints which are preferably disposed in staggered relationship to the inner panel joints. A strap member may be applied to the curved staircase at the upper and lower levels for connection to the building structure.

The inner and outer reinforcing panels may be fabricated from particle board in order to facilitate leading to the curved surface of the side panels of the step modules. Due to its flexible characteristics, the particle board is preferably cut to a height that is twice that of the desired riser height such that individual ones of the inner and outer reinforcing panels are disposed in an abutting edge to edge contact with one another when overlaid upon the side panels.

BRIEF DESCRIPTION OF THE DRAWINGS

These as well as other features of the present invention will become more apparent upon reference to the drawings wherein:

FIG. 1 is a perspective view of a curved staircase of the present invention illustrating a plurality of step modules that are assembled in stacked configuration and which may be interconnected to wall studs of a building structure;

FIG. 2 is a perspective view of one of the step modules comprising a side panel and having a front and back riser extending laterally outwardly therefrom;

FIG. 3 a is a perspective view of the curved staircase illustrating the stacking of step modules to form a plurality of modules joints therebetween;

FIG. 3 b is a perspective view of the curved staircase illustrating a front riser of the step module interconnected to wall studs of the building structure; and

FIG. 4 is a perspective view of the curved staircase illustrating a strap member interconnecting an upper level of the curved staircase to the building structure.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein the showings are for purposes of illustrating the present invention and not for purposes of limiting the same, shown in FIGS. 1-4 is a curved staircase 10 of the present invention which is constructed of pre-manufactured step modules 36. The step modules 36 are assembled in stacked arrangement on top of one another and may be interconnected to a wall such as of a building structure 12. The curved staircase 10 of the present invention is configured as a “inside radius free-standing staircase” wherein an inside radius of the curved staircase 10 is free-standing (i.e., non-supported by a wall) while an outside radius of the curved staircase 10 is interconnected to the building structure 12.

Although the disclosure herein relates to the inside radius free-standing type of curved staircase 10, it is contemplated that the curved staircase 10 of the present invention may be adapted for use as a supported staircase wherein weight-bearing walls extend from both sides of the curved staircase 10. Such weight-bearing walls may be used to enclose a closet, a half bath or a basement stairwell which may be disposed beneath the curved staircase 10 as is common in certain homes.

As will be appreciated, the curved staircase 10 of the present invention is fabricated of pre-formed or pre-manufactured step modules 36 which may be manufactured using unskilled labor with precision tooling and machinery in a climate-controlled facility. Under such controlled conditions, the resulting step modules 36 are produced with tight manufacturing tolerances. Advantageously, the individual step modules 36 may be shipped to the job site at a reduced cost conmpared to the cost of shipping an entire staircase. In addition, the step modules may be assembled in a fraction of the time required to build a conventional curved staircase 10 using conventional on-site construction methods.

In its broadest sense, the curved staircase 10 comprises a plurality of the step modules 36, a plurality of treads 54 mounted on the step modules 36, and a plurality of inner and outer reinforcing panels 58, 62 disposed in overlapping relationship to one another for interconnecting the step modules 36. As can be seen by reference to the figures, the curved staircase 10 extends between upper and lower levels 16, 14 of the building structure 12. The building structure 12 may include framing 24 comprised of a plurality of spaced, vertically-oriented wall studs 26 that extend at least between the upper and lower levels 16, 14 of the building structure 12.

The step modules 36 are specifically adapted to be interconnected to the vertical wall studs 26, either directly or indirectly, so as to provide a load bearing path for an outer radius side of the curved staircase 10. As was earlier mentioned, the inner radius side of the curved staircase 10 is generally free-standing and is supported only at the upper and lower levels 16, 14 of the building structure 12. As will be described in greater detail below, the inner and outer reinforcing panels 58, 62 that are layered over the stacked step modules 36 provide structural rigidity and strength to the assembly such that the inner radius of the curved staircase 10 can support its own weight as well as the weight of persons using the curved staircase 10.

As was earlier mentioned, each one of the step modules 36 is pre-assembled and pre-manufactured using specialized tooling. Likewise, the treads 54 may be pre-manufactured using similar specialized tooling. The step modules 36 and the treads 54 are manufactured as individual components away from the job site under controlled conditions in order to produce a precisely dimensioned component of the curved staircase 10. It is contemplated that the step modules 36, treads 54 and inner and outer reinforcing panels 58, 62 and other components may be shipped directly from the factory to the job site for assembly.

Referring to FIG. 1, shown is the building structure 12 with the curved staircase 10 installed therewith. The building structure 12 may have a framing 24 system comprised of the vertical wall studs 26. As can be seen, the step modules 36 are connected to the vertical wall studs 26. It is contemplated that the vertical wall studs 26 are preferably spaced and oriented so as to be compatible with the joining of the stud modules 36 thereto. However, it is further contemplated that additional blocking 28 may be installed such as to allow for attaching of the step modules 36 thereto should the wall studs 26 be misaligned with the step modules 36.

Each one of the wall studs 26 preferably extends between the upper and lower level 16, 14 although the wall studs 26 may be erected in any orientation or location within the framing 24. The wall studs 26 may extend from the upper level 16 down to the lower level 14 and may be interconnected to the lower level 14 at a baseboard 30 which may be mounted on the lower level (i.e., floor). The baseboard 30 is preferably shaped complementary to the curved staircase 10. More particularly, it is contemplated that the baseboard 30 and, hence, the wall studs 26, are oriented in a curved shape that is compatible with the inner radius of the curved staircase 10. Even more particularly, it is contemplated that the center of curvature of the wall studs 26 which collectively form a radius, is coaxial with the center of curvature of the inner radius of the curved staircase 10. The wall studs 26 are preferably disposed at a spacing to coincide with the angular spacing of the stacked set of step modules 36.

The upper level 16 of the building structure 12 may be fabricated of a series of roof rafters 20 having horizontally-aligned joists. The joists form a support system for a walkway 32 to which the curved staircase 10 leads and attaches. In this regard, the roof rafters 20 (i.e., joists) define the walkway 32 structure 12. The walkway 32 may also include a facia sheet 34 mountd to a side of the walkway 32 and which has a curved shape that is complimentary to the curved shaped of the curved staircase 10. Alternatively, the walkway 32 may be generally straight with the curved staircase 10 blending into the walkway 32 at a tangent of the curved staircase 10 in a smooth transition therebetween.

As can be seen in FIG. 2, each one of the step modules 36 is comprised of at least a side panel 38, a front riser 46 and a back riser 48 which extends outwardly from the side panel 38. The side panel 38 may be generally arcuately shaped (i.e., curved) with a radius of curvature 66 and therefore has an outer convex surface 42 and an inner convex surface. To achieve the particular radius of curvature 66, it is contemplated that the side panel 38 is formed of a plurality of laminated members 40 that are layered over one another. As shown in the figures, the side panel 38 of the step module 36 may be comprised of six laminated members 40 which may be formed of bonded particulate material. The material from which the side panel 38 may be fabricated may be cellulose fiber, shredded paper, wooden particles, sawdust, and various combinations thereof.

The particulate material is bonded together via a matrix resin to form the laminate material. The individual ones of the laminated members 40 may consist of individual thin wooden members made of the particulate material and which are formed around a curved jig. The laminated members 40 may be bonded together in juxtaposition to one another so as to result in a unitary laminated structure 12 having a predetermined size and thickness. Under sufficient temperature, pressure and other conditions, the desired arcuate or circular shape may be formed into the laminated members 40 to result in the side panel 38. As described in U.S. Pat. No. 4,955,168 issued to Barry, the entire contents of which are herein incorporated by reference, a mold may be used to form the side panel 38 in the desired radius of curvature 66. In this regard, the side panels 38 may be formed in any radius and at any length other than that shown in the figures in any suitable manner including the process and materials disclosed in U.S. Pat. No. 4,955,168.

As shown in the figures, the side panels 38 of each one of the step modules 36 may include six of the laminated members 40 being formed of material that is ¼ inch thick in order to arrive at a total thickness of the side panel 38 of 1 and ½ inches. However, any number of laminated members 40 of any thickness may be layered together. The side panel 38 thus forms a partial arch section that has an arc length sufficient for constructing the inner radius of the curved staircase 10.

Each one of the side panels 38 is preferably constructed at a riser height 50 which is preferably the height between each one of the vertical levels of the step modules 36. Such riser height 50 is generally prescribed by local and/or national building codes. Extending laterally outwardly from the outer convex surface 42 of the side panel 38 are the front and back risers 46, 48. As can be seen, the front and back risers 46, 48 are disposed in overlapping relationship to one another and are generally positioned on the outer convex surface 42 at an arc length that is compatible with a tread 54 depth. Similar to the riser height 50, the tread 54 depth may also be controlled by local and/or national building codes.

As can be seen by reference to the figures, the back riser 48 forms the aft mounting surface for the tread 54 while the front riser 46 forms the forward mounting surface for the tread 54 for the step module 36 immediately above. Therefore, the back riser 48 is formed at a riser height 50 that is generally equivalent to that of the side panel 38. More specifically, the side panel 38 and the back riser 48 may each have upper edges that are generally flush with one another such that the tread 54 may be supported by the back riser 48 and the side panel 38 upper edges. The back riser 48 generally abuts the concave outer surface of the side panel 38 and extends laterally outwardly therefrom.

The front riser 46 of each one of the step modules 36 may also have an upper edge which extends upwardly past the upper edges of the side panel 38 and back riser 48 to a level that is equal to that of the riser height 50. In this manner, the front riser 46 of each one of the step modules 36 determines the height of each one of the steps of the curved staircase 10. Therefore, the total height of each one of the front risers 46 is twice that of the side panels 38. More specifically, the side panel 38 and back riser 48 are preferably formed at a riser height 50 while the front riser 46 is formed at twice the riser height 50.

As can be seen by reference to the figures, the front riser 46 may include a notch such that the upper portion of the front riser 46 extends over the upper edge of the side panel 38 and is generally flush with the inner concave surface 44 of the side panel 38. However, it is contemplated that the front riser 46 need not necessarily be flush with the side panel 38 but may be shaped and configured in a variety of configurations. In order to facilitate the attachment of inner and outer reinforcement panels 58, 62 to the curved staircase 10, it is preferable that the end of the front riser 46 is generally flush with the inner concave surface 44 of the side panel 38.

The front riser 46 may be attached to the outer convex surface 42 of the side panel 38 and may have a lower portion that abuts the outer convex surface 42 in a manner similar to that described above for the attachment of the back riser 48 to the outer convex surface 42. It is contemplated that the front and back risers 46, 48 may be attached to the outer convex surface 42 of the side panel 38 by means of glues, adhesives and/or mechanical fasteners such as nails and/or screws. The front and back risers 46, 48 are preferably pre-assembled under controlled conditions at the factory and are then shipped to the job site.

After the step modules 36 have been shipped to the job site, installation thereof is initiated by first connecting the front and back risers 46, 48 to one of the vertical wall studs 26 as shown in the figures. More specifically, the front riser 46 extends laterally outwardly from the side panel 38 and is connected to one of the wall studs 26 on the side thereof. The back riser 48 also extends laterally outwardly from the side panel 38 and is connectable to a front face of the wall stud 26. In certain framing 24 arrangements in the building structure 12 wherein an appropriate vertical wall stud 26 is not readily available adjacent to (i.e., is not aligned with) the front and back risers 46, 48, blocking 28 may be installed into the framing 24 wherein horizontal and/or vertical segments of wooden studs or other material may be framed in between the existing wall studs 26 to create an appropriate attach point that is aligned with the front and back risers 46, 48.

Each one of the step modules 36 is preferably disposed in stacked relationship to one another. In order to create steps for the curved staircase 10, the step modules 36 are disposed in angular spaced orientation with respect to one another. In this regard, the angular spacing and arcuate arrangement of the wall studs 26 is preferably compatible to that of the step modules 36 wherein the angular orientation and spacing between adjacent ones of the step modules 36 matches the angular spacing between the wall studs 26. A module joint 52 is formed between adjacent ones of the step modules 36.

The curved staircase 10 of the present invention further includes the plurality of tapered treads 54 which are mounted on upper edges of the back riser 48 and side panel 38 of respective ones of the step modules 36 and which are further supported and mounted on an upper edge of the front riser 46 of the next lower step module 36. The amount of taper in each one of the treads 54 is formed by the angular orientation of adjacent ones of the front and back risers 46, 48 which extend outwardly from adjacent ones of the step modules 36.

The width or distance of the tread 54 from the outer concave surface of the side panel 38 to the wall studs 26 is preferably equivalent to that of the front and back risers 46, 48. As can be seen in the figures, the step modules 36 are angularly spaced or oriented to create a suitable amount of tread 54 depth that is generally defined by the width of each one of the treads 54. The front and back risers 46, 48 are positioned on the outer convex surface 42 so as to be generally equivalent between a forward end of the side panel 38 and the front riser 46.

In this regard, each one of the treads 54 is preferably mounted so as to be abutted up against the front riser 46 of the step module 36 upon which the tread 54 is mounted. Furthermore, the front riser 46 of the next lower adjacent step module 36 serves as the mounting surface for a forward portion of the tread 54. In order to provide the required nosing 56 that is typical of stair steps, the tread 54 may have an additional material portion that extends slightly over each one of the front risers 46. However, it is contemplated that the nosing 56 may be altogether omited. Alternatively, the nosing 56 may be extended over each one of the front risers 46 in any amount. The nosing 56 may be provided with beveling along the edges thereof.

Regarding specific materials for the tread 54 and the front and back risers 46, 48, manufacturing-grade plywood is preferably utilized as distinguished from construction-grade plywood in order to allow for the retention of tighter tolerances during premanufacturing. However, any grade of plywood may be utilized. In this regard, any wooden or non-wooden material may be used to form the tread 54 and the front and back risers 46, 48, However, manufacturing grade plywood is preferred for the front riser 46 and back riser 48 due to its resistance to ill effects from moisture.

In addition, it is believed that manufacturing grade plywood may retain its tolerances regardless of the amount of moisture absorbed thereinto. Resistance to moisture also insures a better fit of curved staircase 10 when assembled into the building structure 12. Regarding materials from which the treads 54 may be fabricated, it is contemplated that any sufficiently suitably hard and durable wooden or non-wooden material may be utilized. Examples of such materials include, but are not limited to, manufacturing grade plywood and/oror any hard wood such as oak, mahogany, cherry, and birch.

It is contemplated that such individual components including the treads 54 and the front and back risers 46, 48 may be fabricated using specialized tooling and or machinery and may further include the use of computer aided design equipment which may be operatively coupled to such machinery in order to produce parts with a high degree of precision. As was earlier mentioned, such improved precision in dimensional tolerances of the individual components improves the degree to which the curved staircase 10 may be fitted to the building structure 12 in conformance with building codes.

Referring still to the figures, following the stacking and angular spacing of the individual ones of the step modules 36 from the upper level 16 down to the lower level 14 of the building structure 12, a plurality of the inner reinforcing panels 58 is then disposed in overlapping relationship to the inner concave surfaces 44 of the side panels 38 of adjacent ones of the step modules 36. Each one of the inner reinforcing panels 58 overlaps at least one of the module joints 52 to allow for interconnection of the module joints 52.

As shown in the figures, each one of the inner reinforcing panels 58 has generally horizontally disposed edges which abut against one another. A preferable configuration for each one of the inner reinforcing panels 58 is that they are sized to have a width that spans across at least two of the step module joints 52. Furthermore, the inner reinforcing panels 58 may abut one another to form a plurality of inner panel joints 60 which are likewise formed in a horizontal orientation and are preferably disposed in staggered relationship to the module joints 52.

The inner reinforcing panels 58 provide an additional structural load carrying member which transfers loads across adjacent ones of the step modules 36. More specifically, each one of the inner reinforcing panels 58 carries loads across at least one of the module joints 52. As was earlier mentioned, the inner reinforcing panels 58 preferably, but optionally, abut one another to form a plurality of the inner panel joints 60. Such inner panel joints 60 are preferably disposed in staggered relationship to the module joints 52.

A plurality of the outer reinforcing panels 62 are also disposed in overlapping relationship to the inner reinforcing panels 58 and preferably span the inner panel joints 60. More specifically, the outer reinforcing panels 62 provide a structural load-carrying mechanism by which loads are distributed across the inner panel joints 60 to interconnect adjacent ones of the inner reinforcing panels 58. Similar to that described above for the inner reinforcing panels 58, the outer reinforcing panels 62 may also abut one another to form a plurality of outer panel joints 64 which are preferably disposed in staggered relationship to the inner panel joints 60. As shown in the figures, each one of the outer reinforcing panels 62 straddles at least one and, more preferably, two of the inner panel joints 60. The outer reinforcing panels 62 may span any number of inner panel joints 60. The outer reinforcing panels 62 form a plurality of outer panel joints 64 which are then disposed in staggered relationship to the inner panel joints 60. The outer panel joints 64 preferably extend from the lower level 14 to the upper level 16 of a building structure 12.

An additional structural element may be installed at strategic locations on the curved staircase 10 in order to tie the curved staircase 10 to the building structure 12. More specifically, a strap member 22 may be applied to connect the curved staircase 10 to the upper level 16. As was earlier mentioned, the upper level 16 may include a rafter system 18 comprising a plurality of horizontal roof rafters 20 (i.e., joists). This strap member 22 may be attached to an uppermost one of the step modules 36. As shown in the figures, the strap member 22 is attached to the outer reinforcing panel 62 located in overlapping relationship to the uppermost one of the step modules 36. The strap member 22 is horizontally oriented as it attaches to the outer reinforcing panel 62 and then wraps around a lower edge of the side panel 38 and extends upwardly along the outer concave surface of the side panel 38 and interconnects to the upper level 16.

The strap member 22 at the upper level 16 interconnects to at least one of the roof rafters 20 at the upper level 16 adjacent to the uppermost one on the step modules 36. The strap member 22 is preferably of metallic construction but may be formed of any material including non-metallic material. The strap member 22 may include a row of apertures or holes through which mechanical fasteners such as nails or drywall screws may be extended into the outer reinforcing panel 62, inner reinforcing panel 58 and ultimately into the laminated members 40 that make up the side panel 38. At the roof rafter 20, mechanical fasteners such as screws and/or nails may likewise be driven through the apertures and into the roof rafter 20 to firmly attach the curved staircase 10 to the upper level 16 of the building structure 12.

Likewise, at the lower level 14, a strap member 22 may be further provided for connecting the curved staircase 10 to the building structure 12. In a similar manner to that described above for the upper level 16, the strap member 22 may be attached to a lowermost one of the step modules 36 immediately adjacent to the lower level 14 and may extend laterally outwardly along the lower level 14 such as to the floor or deck of the lower level 14. The strap member 22 may likewise be a metallic member with a row of perforations or holes formed therealong through which mechanical fasteners may be extended.

Nails or screws may be driven through the outer reinforcing panel 62, inner reinforcing panel 58 and into the laminated members 40 of the side panel 38 of the step module 36. As can be seen, the strap member 22 may be generally vertically oriented where it attaches to the lowermost one of the step modules 36 and may then bend at a ninety degree angle and extend laterally outwardly along the lower level 14 or it may be attached thereto by use of mechanical fasteners such as screws or nails. It should be noted that the strap member 22 may interconnect the lower level 14 to the curved staircase 10 in any manner.

Regarding materials from which the inner and outer reinforcing panels 58, 62 may be fabricated, it is contemplated that particle board may be utilized. The material may be pre-cut to a desired width and/or length that matches the particular riser height 50 utilized in the curved staircase 10 as installed in the building structure 12. Due to its flexible characteristics, the particle board is preferably cut to a dimension that is twice that of the desired riser height 50 such that individual ones of the inner and outer reinforcing panels 58, 62 may be disposed in abutting edge-to-edge contact with one another when overlaid upon the side panels 38. The inner and outer reinforcing panels 58, 62 may have a length that is intentionally longer than that which is required for the finalized version of the curved staircase 10. In this manner, following completion of installation of the curved staircase 10, the extra length of the inner and outer reinforcing panels 58, 62 may be trimmed simply cut off at an angle that matches the rake or angle of the curved staircase 10 as it extends from the lower level 14 to the upper level 16.

Referring to FIG. 1, during construction of the curved staircase 10 and prior to pre-manufacturing of the individual step modules 36, it is contemplated that markings regarding the curvature of the side panels 38 as well as the curvature or radius of the vertical wall studs 26 may be directly applied to the lower level 14 as a template by which the curved staircase 10 may be measured and installed. More specifically, the desired locations of each one of the step modules 36 may be applied as a radially extending line denoting the front edge of each one of the treads 54. In this manner, measurements of the radius of curvature 66 and tread 54 width may be recorded and used to pre-manufacture the individual components that make up the curved staircase 10 and individual ones of the step modules 36. Furthermore, such radial markings allow for alignment and positioning of individual ones of the vertical wall studs 26 such that the wall studs 26 are generally in alignment with the front and back risers 46, 48 during installation of the curved staircase 10.

Following marking of the construction lines for the curved staircase 10, the side panels 38 may be pre-manufactured at a factory site wherein individual laminated members 40 are joined to one another using the above-described manufacturing process disclosed in U.S. Pat. No. 4,955,168 issued to Barry. Likewise, individual ones of the front and back risers 46, 48 as well as the treads 54 may be further fabricated out of appropriate materials as was earlier discussed in accordance with radius of curvature 66 and angular spacings of the individual ones of the step modules 36.

More particularly, the angular spacings between the step modules 36 defines the tread 54 depth and also defines the dimensions at which the individual ones of the treads 54 are to be held. Following fabrications of the individual components, the front and back risers 46, 48 are joined to one another and are abutted up against the outer convex surface 42. Furthermore, the back riser 48 and side panel 38 upper edges are preferably disposed to be generally flush with one another with the upper edge of the front riser 46 being extended upwardly above the side panel 38 at an amount generally equal to twice the riser height 50. The front and back risers 46, 48 are then glued and/or screwed and/or nailed to the outer convex surface 42of the step panel. The front and back risers 46, 48 are preferably fabricated with a length that is sufficient to be complimentary to the tread 54 width. The treads 54 are preferably fabricated to provide an additional overlap or nosing 56 which is typical of most stairways.

Once the individual step modules 36 are formed, the same are then installed at the building structure 12 in accordance with the markings wherein the individual step modules 36 are stacked in one-at-a-time fashion with the front and back risers 46, 48 being connected via mechanical fasteners and/or adhesive to the adjacent one of the wall studs 26. Once the step modules 36 are stacked from the lower to the upper level 14, 16, the inner reinforcing panels 58 are applied in a manner wherein the inner reinforcing panel 58 straddles at least one of the module joints 52. Following application of the inner reinforcing panels 58 from the lower level 14 to the upper level 16, the outer layer of reinforcing panels is then applied wherein the inner panel joints 60 are covered and straddled by a respective one of the outer reinforcing panels 62.

The extra length of the inner and outer reinforcing panels 58, 62 may then be trimmed off on either side of the inner reinforcing panels 58 (i.e. along a front edge of the panels near the nosing 56 and along a rear edge of the panels). The strap members 22 are applied using adhesives and/or mechanical fasteners or other suitable means to interconnect the curved staircase 10 to the upper level 16 and to the lower level 14 in the manner described above. Following the basic construction of the curved staircase 10, additional operations may be completed to finish off the curved staircase 10 and/or building structure 12. More specifically, balusters and railing may be applied on the inside radius of the curved staircase 10.

Drywalling on the outer radius of curvature 66 of the curved staircase 10 may be applied on the vertical wall studs 26 and other portions of the curved staircase 10. Likewise, any necessary drywalling may be applied underneath the curved staircase 10as well as along the outer reinforcing panels 62. By building the step modules 36 in individual fashion using precision cutting techniques as well as an environmentally controlled condition, a structurally strong and cost-effective curved staircase 10 may be installed in the building structure 12 using unskilled labor with minimal juggling of schedules with framers and/or other finishers.

Additional modifications and improvements of the present invention may also be apparent to those of ordinary skill in the art. Thus, the particular combination of parts described and illustrated herein is intended to represent only certain embodiments of the present invention, and is not intended to serve as limitations of alternative devices within the spirit and scope of the invention. 

1. A curved staircase extending between upper and lower levels of a structure having a plurality of spaced vertical wall studs, the curved staircase comprising: a plurality of step modules each including a side panel, a front riser and a back riser, the front and back risers extending laterally outwardly from the side panel and being connectable to one of the wall studs, each one of the step modules being disposed in stacked relationship to one another to define a plurality of module joints; a plurality of treads mounted on the back riser and side panel of respective ones of the step modules; a plurality of inner reinforcing panels disposed in overlapping relationship to the side panels of adjacent ones of the step modules for interconnection thereof; and a plurality of outer reinforcing panels disposed in overlapping relationship to the inner reinforcing panels for interconnection thereof.
 2. The curved staircase of claim 1 wherein: the side panel is arcuately shaped and having an outer convex surface and an inner concave surface; the front and back risers being disposed in overlapping relation to one another and extending laterally outwardly from the convex surface.
 3. The curved staircase of claim 1 further including: a plurality of treads; wherein: the side panel and back riser of each one of the step modules are formed at a riser height and have upper edges that are generally flush with one another; the front riser of each one of the step modules having an upper edge extending upwardly past the upper edges of the side panel and back riser to a level equal to that of the riser height; the tread of each one of the step modules being mounted on the respective ones of the back riser and on the front riser extending upwardly from the step module located immediately below.
 4. The curved staircase of claim 1 wherein: the wall studs are radially arranged and collectively define a radius of curvature; the side panel having a semi-circular shape that is concentric with the radius of curvature of the wall studs.
 5. The curved staircase of claim 1 further including a strap member connecting the curved staircase to the upper level.
 6. The curved staircase of claim 5 wherein: the upper level includes a rafter system comprising a plurality of horizontal roof rafters; the strap member being attached to an uppermost one of the step modules and wrapping around a lower edge of the side panel and extending upwardly to one of the roof rafters for interconnecting the curved staircase to the upper level.
 7. The curved staircase of claim 1 further including a strap member connecting the curved staircase to the lower level.
 8. The curved staircase of claim 7 wherein the strap member is attached to a lowermost one of the step modules and extending laterally outwardly along the lower level.
 9. The curved staircase of claim 1 wherein the side panel is comprised of a plurality of laminated members.
 10. The curved staircase of claim 1 wherein the side panel is formed of bonded particulate material.
 11. The curved staircase of claim 10 wherein the particulate material is selected from the group consisting of cellulose fiber, shredded paper, wooden particles, sawdust, and combinations thereof.
 12. The curved staircase of claim 1 wherein the front and back risers are fabricated of plywood.
 13. The curved staircase of claim 3 wherein the tread is fabricated of plywood.
 14. A curved staircase extending between upper and lower levels of a structure having a plurality of spaced vertical wall studs, the curved staircase comprising: a plurality of step modules each including a side panel, a front riser and a back riser, the side panel being arcuately shaped and having an outer convex surface and an inner concave surface, the front and back risers extending laterally outwardly from the side panel and being connectable to one of the wall studs, each one of the step modules being disposed in stacked relationship to one another to define a plurality of module joints; a plurality of tapered treads mounted on upper edges of the back riser and side panel of respective ones of the step modules and on an upper edge of the front riser of the next lower step module; and a plurality of inner reinforcing panels disposed in overlapping relationship to the concave surfaces of the side panels of adjacent ones of the step modules for interconnection thereof, the inner reinforcing panels abutting one another to form a plurality of inner panel joints disposed in staggered relationship to the module joints; a plurality of outer reinforcing panels disposed in overlapping relationship to the inner reinforcing panels for interconnecting adjacent ones of the inner reinforcing panels, the outer reinforcing panels abutting one another to form a plurality of outer panel joints disposed in staggered relationship to the inner panel joints.
 15. The curved staircase of claim 14 wherein the side panel is comprised of a plurality of laminated members.
 16. The curved staircase of claim 14 wherein the side panel is formed of bonded particulate material.
 17. The curved staircase of claim 14 wherein the front and back risers are fabricated of plywood.
 18. A step module for forming a curved staircase adjacent to a plurality of vertical wall studs, the step module comprising: an arcuate side panel having an outer convex surface and an inner concave surface; and a front riser and a back riser disposed in overlapping relation to one another and extending laterally outwardly from the convex surface and being connectable to one of the wall studs.
 19. The step module of claim 18 further including: a tread; wherein: the side panel and back riser are formed at a riser height and have upper edges that are generally flush with one another; the front riser extending upwardly past the upper edges of the side panel and back riser to a level equal to that of the riser height; the tread being mounted on the upper edges of the back riser and side panel.
 20. The step module of claim 19 wherein: the wall studs are radially arranged and collectively define a radius of curvature; the side panel having a semi-circular shape that is concentric with the radius of curvature of the wall studs. 